Measurements of effective elastic modulus and microcrack density

Some basic concepts on effective properties of elastic solids containing non-interacting cracks are presented. In the case of one arbitrarily oriented crack in an infinite medium, this approach gives results that coincide with the analysis based on the strain energy of the cracked body. The theories described, as well as other approximate schemes for interacting cracks, are evaluated by conducting well-designed two-dimensional (2D) experiments for measuring effective elastic properties of artificially cracked solids. The tests are performed with aluminum plates subjected to uniaxial tensile stresses, under plane stress conditions. Two different cases are tested, one specimen containing a horizontal crack, perpendicular to the direction of loading, and another containing a number of randomly located cracks. In the second case, the effective properties of the material are presented as a function of crack density. The results show a very good agreement with the non-interacting approximation, even at relatively high values of crack density, where interactions are expected to occur.